Darmian County () is in South Khorasan province, Iran. Its capital is the city of Asadiyeh.
At the 2006 census, the county's population was 51,793 in 12,893 households. The following census in 2011 counted 55,080 people in 14,433 households. At the 2016 census, the county's population was 53,714 in 14,639 households.
Administrative divisions
The population history and structural changes of Darmian County's administrative divisions over three consecutive censuses are shown in the following table. The latest census shows three districts, six rural districts, and four cities.
After the 2016 census, Fakhrud Rural District was separated from Qohestan District, and Miyandasht Rural District from the Central District in the establishment of Miyandasht District. In addition, Nughab Rural District was established in the Central District, and Kushkak Rural District in Qohestan District.